The field of this invention relates to vaccines for hymenoptera stings, or more broadly to allergy vaccines for use in immunotherapy by subcutaneous injection.
Allergic reactions to hymenoptera stings are a serious problem. It has been estimated that nearly 1% of the general population in the United States has a hymenoptera allergy. Each year in the United States, nearly twice as many people die as a result of bites by hymenopteroud insects (including bees, wasps, hornets, and fire ants) than from poisonous snake bites. A majority of systemic reactions and deaths are due to allergic reactions to the venoms of these insects.
Hymenopteran venoms contains histamine, various kinins, and other vasoactive substances, phospholipases, and hyaluronidase. These substances are hemolytic and neurotoxic in addition to being effective hypersensitizing agents. In hypersensitive individuals, a single sting may produce serious anaphylaxis with urticaria, nausea, abdominal cramps, asthma, massive edema of the face and glottis, dyspnea, cyanosis, hypotension, coma, and death. Sensitization is usually the result of previous stings.
Hymenoptera venom preparations are available for clinical use in immunizing sensitive patients. Those approved for use by the Federal Food and Drug Administration include the freeze-dried venom of honey bees (Apis melifera), yellow jacket venom (Vespula sp.), yellow hornet venom (Dolichovespula arenaria), white-faced hornet venom (Dolichovespula maculata), and wasp venom (Polistes sp.). These venom preparations contain the allergenic protein of the hymenoptera venom in water-soluble form, and are dissolved in a suitable aqueous vehicle for subcutaneous administration.
Fire ants are another stingy insect of the order of hymemoptera. Allergic reactions are commonly experienced after fire ant stings. For diagnostic purposes, extracts of the whole bodies of fire ants have been used as well as the fire ant venom. The antigens responsible for the allergic reaction appear to be present in both preparations. Heretofore, immunotherapy has employed whole body fire ant extracts.
Clinically, immunization with the available hymenoptera venom preparations described above can be painful and protracted, and the injections must be given with extreme care to avoid adverse effects. To guard against anaphylaxis with sensitized patients, the initial injections must be given at a very low level, and injections must be administered at frequent intervals with progressively increasing dose levels. For example, the initial injection may contain 0.05 micrograms or less of venom protein, and after a series of up to fifteen injections, the dose level may reach 100 micrograms. A single hymenoptera sting, such as a bee sting, corresponds on the average to about 100 micrograms of venom protein. Therefore, it can be seen that the present practice of immunization begins the injections at much less than the level corresponding to one sting, such as 1/20 of a sting, while the maintenance immunization level of about 1 sting may be reached after a long series of injections.
It would be desirable to provide hymenoptera venom vaccines which can be administered at higher dose levels without undue risks to sensitive patients, thereby making it possible to reduce the number of doses required for immunization. Further, if the immunizing doses can be carried to a higher level so that a more complete immunization is obtained, subsequent maintenance injections can be given at longer intervals, and the maintenance injections can also be at higher dose levels increasing their immunizing effectiveness. It is known that immunizing vaccines of reduced allergenicity can be prepared from pollens by reacting the allergen with glutaraldehyde. Patterson et al, J. Immunol., 110: 1413-1417 (1973); Patterson et al, J. Allergy Clin. Immunol., 59: 314-319 (1977). It is also known that proteins may be reacted with glutaraldehyde to form either water-soluble or water-insoluble polymers. See Immunochemistry (1969), Vol. 6, 53-66, Avrameas et al. U.S. Pat. No. 3,794,630 discloses pollens polymerized with glutaraldehyde in a substantially water-insoluble form.
Heretofore, very little has been published on polymerized or chemically modified hymenoptera venoms. Boehm et al reported in 1977 that they obtained an insoluble product by reacting formaldehyde with bee venom, but that they were able to obtain a soluble product by reacting glutaraldehyde with bee venom. The water-soluble glutaraldehyde polymer of bee venom was found to have antigenic activity and reduced toxicity. Boehm et al, Abstract 17, Abstracts of Scientific Papers, American Congress of Allergy and Immunology, Mar. 23-31, 1977, New York, NY. Subsequently, the same research group has reported that chemically modified bee venom in water-soluble form was prepared in three different ways: (1) polymerization with formaldehyde, (2) acetoacetylation, and (3) coupling to polyethylene glycol. Mueller et al, Abstract 126, Abstracts of Papers, 36th Annular Meeting of The American Acedemy of Allergy, Feb. 18-20, 1980, Atlanta, Ga.
Patterson et al attempted to prepare a soluble polymer of bee venom by glutaraldehyde treatment, as had been done with ragweed antigen E, and grass and tree pollen allergens. However, multiple experiments using variations in concentration of glutaraldehyde, reaction time, and temperature produced either no polymerization or the formation of a solid polymer product. J. Allergy. Clin. Immunol., 66: 495-499 (1980). A micronized form of the insoluble bee venom polymer was found to be antigenic in rabbits. Subsequently similar insoluble preparations were made from other hymenoptera venoms and human clinical trials were initiated. IgG response to the respective venoms used occurred in the sensitive patients without local or systemic allergic reactions, but the IgG response was of low magnitude and short duration. Patterson et al concluded that polymerized insoluble venoms were safe but had not demonstrated efficacy and terminated this approach. (Unpublished findings.) Many other approaches were then tried for preparation of glutaraldehyde polymers of hymenoptera venoms in soluble form but without success prior to the present invention.